Near-Ideal Subthreshold Swing in Scaled 2D Transistors: The Critical Role of Monolayer hBN Passivation

Hexagonal boron nitride (hBN) has been envisioned as an ideal two-dimensional (2D) dielectric for 2D transistors due to its natural match in dimensionality and exceptional thermal properties. However, its small bandgap and dielectric constant precludes its use in ultra-scaled, high-performance electronics. In this study, we experimentally identify the roles of monolayer hBN (1L-hBN) in scaled 2D transistors. Our results demonstrate that 1L-hBN can function as a passivation layer to minimize the trap states from the environment, enabling near-ideal subthreshold swing (SS ~62 mV/dec) and a narrow distribution with a standard deviation (
$\sigma $
) of 4.4 mV/dec in short-channel monolayer molybdenum disulfide (1L-MoS2) transistors. Additionally, we found that 1L-hBN can serve as a crystalline interfacial layer (IL) to mitigate damages caused by high-
$\kappa $
dielectric stack integration. These findings collectively unveil the potential of 2D crystalline hBN for realizing high-performance 2D transistors.